The mistress (or master) is the name given to the dominant woman in a master/slave or dominant/submissive relationship. The activities that are performed are the same as a dominatrix, but an ongoing relationship may be what is implied with a mistress, allowing the development and exploration of the dominant and submissive paradigm.
Yes. This is NOT a prostitution or escorting site. There are NO sexual services on offer from any of the dominatrixes and they offer the highest degree of privacy and professionalism.
Depends on what you want. There are many types of domination and submission out there.